I don't recall off hand if the 757 has a RAT or not. But the fact that it's a all-hydraulic airplane doesn't mean a RAT is necessary. The 747 is all hydraulic, and prior to the -8 it never had a RAT - it wasn't needed. In the case of an all engine out event (and there have been a handful of 747 all-engine out events) there is sufficient hydraulic pressure provided by the windmilling engines to provide control of the aircraft.
Since the 747 all engine out events that I can recall had happy endings (volcanic ash encounters) the Boeing engineers apparently got it right.
The 747-8/8F did get a RAT - the combination of greater hydraulic requirements (due to the new wing) and engines that windmilled slower (big fan/small core) meant a RAT was needed.